Conventionally, shoulder straps installed in shoulder bags have exhibited a problem of slipping off easily. In order to prevent such shoulder strap from slipping off, there has been disclosed a slippage prevention device in which one end thereof is to be fixed to the shoulder strap, and the other end thereof is to be directly latched onto a certain part of a user's body such as the neck, a lower armpit region and the like (e.g. Patent document 1).